Coprecipitation synthesis of Ca 14 Al 10 Zn 6 O 35 :Mn 4+ deep‐red phosphor and silica‐modified waterproofing ability

Ca 14 Al 10 Zn 6 O 35 :Mn 4+ (CAZ:Mn) phosphor material, which shows deep‐red luminescence, was synthesized by the coprecipitation (COP) method using a Na 2 CO 3 /NaOH solution as the precipitant. COP–CAZ:Mn phosphor exhibited a 2.1 times higher luminescence intensity than the corresponding phosphor prepared using the conventional solid‐state reaction (SSR) method. This substantial increase in luminescence was mainly ascribed to the existence of a greater proportion of tetravalent manganese in COP–CAZ:Mn phosphor. Furthermore, COP–CAZ:Mn phosphor was modified with SiO 2 via hydrolysis of tetraethoxysilane (TEOS) to waterproof the compound because it is easily decomposed through hydrolysis under humid conditions. The SiO 2 ‐modified CAZ:Mn phosphor maintained its crystal structure and high photoluminescence intensity after the water‐resistance test. Therefore, waterproof CAZ:Mn phosphor with a high luminescence intensity was successfully discovered by utilizing the coprecipitation method and SiO 2 modification.